How the BMW X6 ActiveHybrid Works

Buying a car is often about compromises. If you want something that's safe and can haul your family and groceries, this often comes at the expense of sporty handling and performance. Or you may desire better fuel economy, yet this typically means getting a smaller, more efficient vehicle. There are actually very few cars on the market that can offer a perfect combination of everything we want.

However, carmakers are finding ways for buyers to not have to live with sacrifices. In fact, many of BMW's cars fall along these lines: SUVs and sedans that offer performance, handling, room and in some cases, they're even good for the environment. Recently the company has been focused on creating high-tech gas and diesel engines that have very low emissions.

A few years ago, BMW came out of left field with the extremely unusual-looking X6 model, a vehicle that blurred the lines between SUV, hatchback and sports car. The vehicle's long, sloping roof line gives it the look of a sports coupe, but it rides tall on big tires and it's also a highly capable off-roader. It's an SUV, yes, but one with eye-catching style and potent acceleration from its turbocharged six- and eight-cylinder engines. At the same time, the X6 boasts a substantial amount of cargo space.

The German automaker even makes a highly tuned version called the X6 M, with a 555-horsepower V8 that's as fast as the last-generation M3 sport sedan [source: Wert].

Still, all this fun, style and utility come at the expense of one thing: fuel economy. While the regular X6 with a V8 engine gets about 12 miles per gallon (5.1 kilometers per liter) in the city and a mere 18 miles per gallon (7.7 kilometers per liter) on the highway; the high-performance M version will likely fare even worse.

But what if it didn't have to be that way? Can you have your cake and eat it too? BMW thinks so, and that's why they built the BMW X6 ActiveHybrid concept car.

Hybrids use gasoline or diesel engines coupled with an electric motor to boost fuel economy and reduce emissions. This technology is finding its way into several different types of vehicles, including big ones and fast ones, too.

In this article, we'll look at the hybrid version of BMW's unusual performance SUV, and show how advanced technology will help the X6 ActiveHybrid achieve better fuel economy over the standard version -- and create what BMW calls "Efficient Dynamics."

BMW X6 ActiveHybrid Design

Like the ordinary, non-hybrid X6 model, the BMW X6 ActiveHybrid's exterior design is the first thing people will notice. Similar to the Volkswagen CC and Mercedes-Benz CLS, it uses a curving roof line to give off an aggressive, sports car-like look. In fact, BMW doesn't call it an SUV, but rather a "Sports Activity Coupe" -- despite having four doors and not two.

The X6 rides on big, 21-inch tires and has a unique front bumper that adds to its powerful look. It's not for everyone, though -- the car's looks have been equally praised and criticized in the automotive press.

The car is mechanically similar to BMW's more conventional SUV, the X5, but the curvy roof comes at the cost of some rear headroom and hauling ability. The X6 only seats four people in two rows of seats, as opposed to the X5's three rows. The X6 is also lower and longer than the X5.

Inside, the X6 has a number of high-tech features. Its gear selector looks more like a video-game joystick, where the driver can toggle it up and down to select different gears. There's also the latest version of BMW's iDrive, a knob and computer screen that lets the driver control the audio, climate and navigation systems.

The car also has a number of unique safety features designed to make it confident on every kind of road surface. The X6's xDrive all-wheel-drive system and Dynamic Performance Control distributes the engine's power between any of the four wheels depending on conditions. This allows the car to have more agile and exact handling than you'd expect from a car that weighs more than 5,000 pounds (2,268 kilograms) [source: Emmerson].

The hybrid concept, unveiled at the 2007 Frankfurt Auto Show, boasts some unusual features that accentuate its ability to run on electric power. For example, aluminum plates underneath the car move out to cover up the exhaust tips when the car is running solely on the electric motor [source: Automobile Magazine].

In the next section, we'll find out what makes the BMW X6 ActiveHybrid tick, and how its electric motor is used to boost both fuel economy and performance.

BMW X6 ActiveHybrid Specs

The BMW X6 ActiveHybrid concept uses "Efficient Dynamics" to create a vehicle that's not only fun to drive, but also fuel efficient.

Courtesy of BMW USA

While the conventional X6 that's currently on-sale is powered by a 300-horsepower, twin-turbo inline six-cylinder engine or a 400-horsepower V8, the hybrid relies solely on a V8 with two electric motors attached.

The hybrid system on the X6 is described as a two-mode hybrid system -- a complex mechanism developed jointly by General Motors, BMW and Daimler. The system uses three gearsets in the transmission that split power between the gasoline engine and the two electric motors. The two electric motors are run by a large battery pack.

The transmission determines when the car should run on electric power, gasoline or a combination of the two. It's ideal for SUVs because of its ability to pull large amounts of weight, and has actually been used on GM transit buses for years [source: Stahl].

On the X6 ActiveHybrid, the two-mode system means just that: one transmission mode that uses the electric motors for maximum efficiency while pulling away from a stop and low-speed driving, plus a second mode that's ideal for high speeds and bursts of acceleration [source: BMW.com]. The brakes also capture kinetic energy during deceleration to recharge the battery pack.

The goal of this is to create what BMW calls "Efficient Dynamics," or a vehicle that is exhilarating to drive without sacrificing fuel economy. They hope to combine the best assets of electric and gasoline engines to create new levels of performance -- for example, taking advantage of the fact that electric motors hit their peak torque instantly from a standstill. With the gasoline engine providing power at higher speeds, a fast car is created that requires less fuel to achieve high performance [source: BMW.com].

All this technology is expected to increase the X6's fuel economy by up to 20 percent. While mile-per-gallon and horsepower figures haven't been released by BMW just yet, a 20 percent increase in fuel economy over the standard V8 would mean the BMW X6 ActiveHybrid could achieve nearly 22 miles per gallon (about 9.4 kilometers per liter) on the highway. That's a respectable figure for a car that weighs so much and puts an emphasis on spirited driving, as well.

As mentioned before, there are always tradeoffs involved. The ActiveHybrid system will add both weight and additional cost to the X6. However, the concept -- possibly set to be in production by 2010 -- shows that perhaps we can have vehicles that can do it all, from SUV capability to performance and even Earth-friendly emissions levels.

For more information about the BMW X6 ActiveHybrid and other hybrid car topics, follow the links on the next page.